This invention relates to an improved process for producing lube oil. More particularly, it relates to a process for producing a sunlight-stable lube oil blend in the absence of a hydrotreating or hydrogenation step.
Raw hydrocrackate lube oil stocks obtained by hydrocracking heavy oils are known for their poor sunlight stability. Consequently, common practice is to process the hydrocrackate, for example by a sequential hydrogenation, and thereby improve its stability. However, each additional step, especially a hydrogenation step in the production of a lube oil, adds to its already substantial cost.
In U.S. Pat. Nos. 3,530,061 (D. A. Orkin et at) and 3,852,207 (B. E. Stangeland et al) are disclosed combination hydrocracking and hydrogenation processes for the production of lube oils from heavy oils.
It is known in commercial practice to produce sunlight-stable lube oils by solvent-extracting a gas oil without employing a hydrogenation step (see, for example, Petroleum Processing Handbook, McGraw-Hill Book Company, William F. Bland and Robert L. Davidson, Co-editors, Sections 3-79 to 3-82, inclusive, and 3-86 to 3-92, inclusive, which are incorporated herein by reference). While such practice is advantageous, there is need for improvements, for example in terms of reduced cost and enhanced production capacity without a corresponding capital outlay for expanded facilities.
It is an object herein to provide an improved process for producing a sunlight-stable lube oil blend from gas oil lube oil stocks and raw hydrocrackate lube oil stocks.
A further object is to provide improvements, for example at reduced costs and with improved yield, in a lube blending process without including a hydrotreating or hydrogenation step in the process.
These and other objects will be clear from the description and examples to follow.